This research is aimed at describing in isolated osteroclasts the cytoskeletal components, the subcellular location and function of several enzymes, the elemental composition, and the mitochondrial activity. These aspects of cell biology will be examined in different hormonal environments. To accomplish this we will employ the techniques of indirect immunofluorescent antibody microscopy, electron microprobe analysis, and fluorescence microscopy. The several aspects of osteoclast structure, composition and function we propose to investigate should provide further information for establishing a more rational basis in designing therapeutic measures directed at metabolic diseases of the skeleton.